Catalytic role of binary oxides (CuO and Al2O3) on hydrogen storage in MgH2

Abstract Hydrogen sorption characteristics of magnesium hydride (MgH 2 ) were enhanced by ball milling for 12 h under an inert atmosphere with the addition of 20 wt% Al 2 O 3 and as prepared CuO. X‐ray diffraction (XRD) characterization and thermal gravimetric analyzer coupled with a mass spectrometer (TGA‐MS) of the ball milled samples were carried out to determine the H 2 sorption reactions. Additionally, XRD data were analyzed using Rietveld method to identify the crystallographic properties. Ball milled MgH 2 with β and γ allotrope mixtures were found with broad peaks in XRD indicating the as prepared samples are amorphous and strain, alongside bare additives. H 2 sorption in MgH 2 is greatly enhanced by the presence of CuO and Al 2 O 3 binary oxides. TGA experiment demonstrated fast desorption kinetics for ball milled samples with the oxide additives. Particularly, MgH 2 milled with CuO showed a more remarkable effect on desorption kinetics rather than Al 2 O 3 . It takes less than 10 min to desorb more than 5 wt% H 2 at 623 K. The activation energy of H 2 desorption was estimated for the mixtures by Kissinger method and the lowest value (65 kJ mol −1 ) was obtained for the MgH 2 /CuO mixture. A kinetic model has been proposed in the context to illustrate the complex mechanism of dehydrogenation of MgH 2 with the additives. Finally, the addition of metal oxides influences H 2 sorption characteristics of MgH 2 through lowering the activation energy and reducing the waste of energy for diffusing the thin layer of Mg that creates a pathway to store H 2 within the system.